Even though scholars have expressed strong concerns about judges’ use of legal fictions and some have warned of potential “dangers” of legal fictions, no one has yet elaborated on exactly how we can recognize a “dangerous” legal fiction. Building on existing scholarship on legal fictions and the empirical psychological research about human decision making processes, my article contributes to the discussion by offering a systematic approach to distinguishing a benign from a dangerous legal fiction. This article suggests that a benign fiction comes with some built in reminders of its fictional nature while a dangerous fiction does not. A fiction may be benign or dangerous depending on the presence of any of the following characteristics: Whether or not (1) the fiction is labeled explicitly as a fiction; (2) the fiction rests on complete factual falsity instead of reduction of evidentiary proof; (3) the fiction allows the court to reach a result inconsistent with a relevant fundamental principle instead of consistency with well-established principles. The presence of those factors make the user aware that the doctrine is a fiction and offers a safeguard against its excessive use, making the legal fiction a benign one. Without those reminders, a legal fiction can become “dangerous.” Lack of reminders makes it more likely that judges may use legal fictions for purposes not intended to be served by the doctrine. The article uses the consent fiction in contract law as an example of how a legal fiction can be dangerous.